Field of the Invention
The invention relates to a process for producing ultra-pure water for a semiconductor manufacturing plant via water treatment and purification steps and to water treatment configuration for carrying out the process.
Semiconductor manufacturing plants of this nature may be configured in particular as plants for processing wafers, in which case a plant of this nature contains a large number of manufacturing units. The individual manufacturing units form one or more process lines, a certain type of wafer processing being carried out in each of the manufacturing units.
Inter alia, large amounts of ultra-pure water are required for the processing steps carried out in the individual manufacturing units. In known semiconductor manufacturing plants, an ultra-pure water treatment plant is provided for producing the ultra-pure water. In the ultra-pure water treatment plant of this nature, the ultra-pure water is obtained in a plurality of purification steps. First, preliminary purification of untreated water takes place in a pretreatment step, the untreated water usually consisting of municipal water which is supplied from the surrounding district. As an alternative, spring water may also be used. The preliminary purification is carried out as a function of the parameters of the untreated water. Then, the water that has undergone preliminary purification is purified further in a treatment step, in which purification takes place substantially independently of the process parameters of the untreated water. This purification step alone eliminates a large proportion of the contaminants from the water. The treated water that has been obtained in this way finally undergoes final purification in a last purification step, known as polishing.
The ultra-pure water is used to supply the entire semiconductor manufacturing plant. In this case, it is preferable to provide a ring pipeline system that connects the ultra-pure water treatment plant to the individual manufacturing units of the semiconductor manufacturing plant. In the ultra-pure water treatment plant, ultra-pure water is provided in sufficient quantity and with a sufficiently high purity according to the total quantity and the purity required in the semiconductor manufacturing plant. Typical ultra-pure water parameters in this context are oxygen content, a total organic carbon (TOC) levels, a metal content and a concentration of particles and microorganisms.
Since the requirements imposed on the purity level of the ultra-pure water are extremely high yet large quantities of ultra-pure water are required, ultra-pure water treatment plants of this nature are highly complex and, in particular, also very expensive.
Japanese Patent JP 631 08 724 discloses a configuration for producing ultra-pure water, which has a central first purification step for obtaining primary pure water from untreated water. The primary pure water obtained in this way is fed to various final purification units via a plurality of feed lines, each of which units are used to produce the ultra-pure water. The ultra-pure water is fed to cleaning appliances via feed lines made from ethylene fluoride.
The decentralized production of the ultra-pure water in the final purification steps and the conveying of the ultra-pure water in feed lines made from ethylene fluoride to the cleaning appliances ensures that the quality of the ultra-pure water does not deteriorate between a final purification unit and a cleaning appliance. However, a drawback of the configuration is that large quantities of pure water are produced centrally in the purification step, and this water is supplied to the decentralized final purification steps. A further drawback is that the ultra-pure water is produced in the same quantity in the final purification steps. A configuration of this nature is correspondingly complex and expensive.
It is accordingly an object of the invention to provide a process for producing ultra-pure water, and a configuration for carrying out a process of this nature which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, in which the ultra-pure water for semiconductor manufacturing plants is produced as simply and inexpensive as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, a process for producing ultra-pure water for a semiconductor manufacturing plant having a plurality of manufacturing units, which includes:
treating an amount of untreated water required for the semiconductor manufacturing plant in a first purification stage resulting in treated water; and
feeding the treated water obtained at an outlet of the first purification stage to a plurality of final purification units (8) which are each associated with at least one of the manufacturing units, the ultra-pure water being obtained from the treated water in a second purification stage in each of the final purification units, the ultra-pure water obtained in each of the final purification units undergoing final purification to a stipulated purity level in dependence on process parameters of an associated one of the manufacturing units.
The basic concept of the invention consists in providing a central water treatment plant in order to prepare the ultra-pure water for the semiconductor manufacturing plant, by use of which water treatment plant treated water is obtained from untreated water in a first purification step. Advantageously, the first purification step is subdivided into a preliminary purification (pretreatment) step followed by further treatment.
The treated water is fed to a plurality of decentralized final purification units via a pipeline system. Each of these final purification units is assigned to supply ultra-pure water to one manufacturing unit or a group of manufacturing units of the semiconductor manufacturing plant.
In each final purification unit, the ultra-pure water for the respectively associated manufacturing units undergoes final purification in accordance with the purity level required for those units on an individual basis.
Consequently, the purity level (quality) of the ultra-pure water obtained in the individual final purification units varies as a function of process parameters of the manufacturing units which are in each case assigned to a final purification unit. The purity level of the ultra-pure water produced in each final purification unit is in this case stipulated by parameters of the ultra-pure water.
Therefore, the decentralized final purification of the ultra-pure water makes it possible to precisely match the parameters of the ultra-pure water and therefore the purity level of the ultra-pure water to the different requirements in the individual manufacturing units. By comparison with a central final purification step, this considerably reduces the complexity and costs for obtaining the ultra-pure water.
This is based primarily on the fact that the ultra-pure water obtained in a central final purification step must satisfy the purity requirements of all the manufacturing units in the plant. The requirements imposed on the purity of the ultra-pure water are correspondingly high. In addition, this high-quality ultra-pure water is required in very large quantities, since it has to be fed to all the manufacturing units that need water.
By contrast, if the ultra-pure water is supplied according to the invention, only treated water is produced in the central treatment plant. obtaining treated water entails relatively little material expenditure and low costs.
Feeding the treated water to the individual final purification steps also does not involve high costs, since the requirements imposed on the materials of the pipeline system required for this purpose are low.
Finally, the final purification in each final purification step takes place only in accordance with the minimum requirements that are imposed by the process parameters of the associated manufacturing units. In some cases, these requirements may be so low that the final purification operation may even be dispensed with altogether for certain manufacturing units. This prevents ultra-pure water of very high quality being used for those manufacturing units for which ultra-pure water of lower quality would be sufficient. Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a process for producing ultra-pure water, and a configuration for carrying out a process of this nature, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.